In a wideband wireless access system, a bandwidth request method is classified into a contention-based request scheme and a contention-free request scheme. In the contention-based request scheme, a plurality of users contends for a bandwidth request in one channel. In the contention-free request scheme, a bandwidth request is transmitted through a channel allocated to each user. When using the contention-free request scheme, a mobile station may transmit a bandwidth request message through a channel allocated by polling of a base station via unicast or may transmit the bandwidth request message by being piggybacked on a remaining region of a previously allocated bandwidth.
FIG. 1 illustrates a procedure for allocating an uplink resource to a mobile station using a contention-based request scheme.
A mobile station (MS) transmits a randomly selected code division multiple access (CDMA) code via a randomly selected slot in a region allocated for a bandwidth request (step 110).
Upon recognizing the CDMA code transmitted from the MS, a base station (BS) allocates, using a CDMA allocation information element (IE), a resource for transmitting a bandwidth request message to the MS (step 120). The MS then transmits the bandwidth request (BW_REQ) message using the corresponding resource region (step 130). The bandwidth request message includes information on a size of a requested bandwidth. If the bandwidth requested by the MS is available, the BS allocates an uplink resource (step 140). The MS transmits data using the allocated uplink resource (step 150).
FIG. 2 illustrates a procedure for allocating an uplink resource to an MS using polling in a contention-free request scheme.
A BS periodically allocates an uplink resource for transmitting a bandwidth request message to the MS (step 210).
The MS transmits, to the BS, the bandwidth request message including information on a bandwidth corresponding to a size of data to be transmitted by the MS (step 230).
If the bandwidth requested by the MS is available, the BS allocates an uplink resource (step 240). The MS transmits data using the allocated uplink region (step 250).
The conventional contention-based request scheme includes a three-step procedure, i.e. a transmission of CDMA code, an allocation of a resource for BW-REQ and a transmission of BW-REQ. The first step may cause a collision and thus this contention-based scheme is not proper to transmit signaling information or traffic which is sensitive to delay. In the polling scheme, as the number of mobile stations receiving polling increase, a resource for transmitting the bandwidth request message (minimum 3 bytes×8=24 bits) and signaling information for indicating the resource increase.